1. Field of the Invention
This invention relates to the processing of semiconductor materials. More particularly, this invention relates to the treatment of a semiconductor substrate with one or more group IV elements to inhibit migration of dopant materials in the semiconductor substrate, and the resulting treated semiconductor substrate product.
2. Description of the Related Art
In the formation of semiconductor devices such as integrated circuit structures on a semiconductor substrate, such as, for example, a silicon wafer, dopant materials are conventionally added to the single crystal semiconductor substrate, usually by implantation and/or diffusion of the dopant material into the single crystal lattice to respectively provide an excess of one type of charge carrier, comprising either holes or electrons, in the crystal lattice, depending upon whether either p-type or n-type semiconductor material is desired. Typically, for example, a group IV semiconductor substrate such as silicon or germanium is doped with boron to provide a p-type semiconductor material, or is doped with phosphorus or arsenic to provide an n-type semiconductor material.
However, not only is the type of doping of the semiconductor substrate important, but the extent or concentration of the doping is also important for many applications or uses of doped semiconductor materials, for example, to achieve a lightly doped p-region, a p region, or a p+ region. For example, one may wish to construct a p channel or PMOS device comprising p+ source and drain regions in an n type well in a p- silicon semiconductor with p- lightly doped portions (ldds) between the heavily doped p+ drain region and the n doped channel beneath the gate electrode. Thus, the maintaining of different levels of dopant concentrations in various portions of a semiconductor material is also important to the performance of active devices made utilizing such doped regions of varying concentration. Therefore, after initial doping of a region of a semiconductor material, e.g., by an implantation procedure, it is very important that the migration of the dopant material out of the doped region be prevented, or at least inhibited.
Since the formation of semiconductor devices such as integrated circuit structures require a number of steps, including many steps involving the heating of the semiconductor substrate, and migration or diffusion of dopant materials through a semiconductor substrate is known to be accelerated with rises in temperature, it is often difficult to maintain a given concentration of dopant in a particular region without excessive migration. Even the initial doping of the substrate is usually carried out by means (implantation) which requires subsequent annealing of the implanted semiconductor material at elevated temperatures to repair the damage done to the crystal lattice of the semiconductor material during the implantation step. Often it is, therefore, necessary to dope a substrate at a higher than desired concentration in order to compensate for dopant losses which will unavoidably occur by migration in order to achieve a particular desired final concentration of dopant in a given region after completion of the processing of the semiconductor substrate.
Kase et al. in "Eliminating Channeling Tail by Lower Dose Preimplantation", published in Applied Physics Letters 56 (13), 26 Mar. 1990, at pp. 1231-1232, describe the implantation of a silicon substrate with either silicon or germanium and its effect on channeling of implanted boron. In a later publication Kase et al., in "BF.sub.2.sup.+ Implantation in Predamaged Si with Ge.sup.+ or Si.sup.+ at Doses Lower than Amorphization", published in the Journal of the Electrochemical Society, Volume 138, No. 10, October 1991, at pp. 550-554, describe what was apparently an initial increase in boron diffusion resulting from such an implantation of a silicon substrate with silicon, and the authors note that subsequent increases in the concentration of the silicon implantation until amorphization is reached resulted in reductions of the boron diffusion rate.
However, It would be desirable if one could, during and after implantation of a dopant material in a particular region of a semiconductor substrate, reliably control and inhibit migration of the dopant material from the doped region of the semiconductor substrate, by either channeling or diffusion, during the processing of the substrate.